Views:4 Author:Site Editor Publish Time: 2019-10-16 Origin:Site
Common flame retardancy tests include burn test, limiting oxygen index, glow wire test, smoke test and so on. The purpose of the flame retardant test is to evaluate the combustion characteristics of the material, that is, to test the sample by simulating the actual combustion conditions, and to evaluate the combustion characteristics of the sample from different dimensions such as ignitability, light-off property, smoke generation, and flame retardancy.
1. Combustion test
Combustion testing refers to igniting a sample by means of an open flame, and comprehensively assessing the flammability of the sample based on indicators such as burning speed, flame duration, and presence or absence of drip. UL 94 is widely used in the flame retardant evaluation of various materials due to its scientific evaluation method and universality. A large part of the combustion test standards are cited and improved based on the UL 94 combustion evaluation method.
2. Limiting oxygen index test
The limiting oxygen index evaluates the flammability of the sample and, under the specified test conditions, measures the minimum oxygen concentration that just maintains the material's combustion. The test method is to fix the sample vertically in the combustion cylinder and fill it with a certain concentration of oxygen and nitrogen, ignite the top of the sample with an igniter, observe the combustion condition of the sample, and adjust the oxygen concentration accordingly until the sample is just the lowest at the equilibrium combustion. Oxygen concentration is shown as a percentage of oxygen content.
3. Glow wire test
The glow wire test test simulates whether the high-heat metal wire core generated in the short circuit of the polymer case inside the electronic device causes combustion and ignition of the outer casing. The glow wire itself is a fixed-size resistance wire ring. It is electrically heated to the specified temperature during the test. It is the time required for the top of the glow wire to contact the sample to meet the standard requirements and observe the light-off condition. There are two types of indicators for the glow wire test, the flammability index GWIT and the ignitability temperature GWIT, and the evaluation indicators are different.
4. Smoke test
The polymer has a long carbon chain and requires a large amount of oxygen during combustion. The oxygen concentration in daily life is difficult to support the complete combustion of the sample, but not completely burned back to produce a lot of harmful substances such as carbon monoxide and benzene which are harmful to the human body and the environment. substance. When the smoke test is carried out, the sample is fixed in the box, and the electric heating is used to burn the sample in the box to generate smoke, and the change of the transmittance of the equal beam passing through the smoke is measured, and the specific optical density, that is, the unit area is calculated. The smoke generated by the sample diffuses in the smoke density of the unit light path length per unit volume of the cigarette case.
In addition to the above conventional flame retardant tests, there are also a large number of finished product standards for building materials, rail transit, wire and cable, etc. These tests will be tested according to specific applications, such as cigarette ignition test, smoldering test, Tobacco toxicity test, heat radiation flux test, etc.